I don't know if someone has requested this function before, but it would be nice to have a calendarfunction where you could enter all the national holidays in YYMMDD format, and in the Schedule select if you would like to treat the days in the calendar as checked or nonchecked.
You don't like how list of holidays implemented in HostMonitor 4? Or you just missed this option? In this case open Schedules dialog and click "Holidays" button.